Prepare brownie mix and bake according to package directions in a 13 x 9-inch pan.,______,Prepare chocolate mousse according to directions, omitting chilling.,Place half of brownies in bottom of a 3-quart trifle dish and top with half of mousse, crushed candy bars and whipped topping.,Repeat layers, ending with whipped topping.,Garnish.,Chill at least 8 hours.